Induction electric furnace construction



m13,1 932. REEL" 1,890,773

I-Nnucnou ELECTRIC FURNACE cous'rnucnou Filed June so; 1930 I II - VIII, I a I ,VII'I'II'I 'IIIIII; 'IIIIIIIII Patented Dec. 13, 1932 UNITED STATES PATENT OFFICE FRANZ EIBL, OI' FINOW, GERMANY, ASSIGNOR TQ AJAXELECTROTHERMIC CORPORA- T1017, 01 AJAX PARK, NEW JERSEY, A CORPORATION OF NEW JERSEY nmuc'rron nnnc'rmo rummcr. con's'rmro'rron Application filed June so, 1930, Serial no. 464,8 08, and in Germany December 31, 1929.

My invention relates to water cooled in-. ductor coils for electric furnaces.

A' purpose of my invention is to form an inductor coil having an interior water carrying passage whose walls are initially continuous throughout, without the necessity of dering, brazing, or otherwise.

A further purpose isto fold longitudinally continuous tubing so as to concentrate a considerable'part of the metal at one side of the tubing and leave an interior passage at the other side, and to wind the tubing with the folded side inward to form a water cooled inductor coil.

A further purpose is to avoid danger of leakage from a water cooled inductor coil under conditions ofabnormally high heat- 1ng.

Further purposes will appear in the specification and in the claims.

It has previously been recognized that the current density per unit cross sectional area in an inductor coil of an induction furnace increases from a minimum near the periphery to a maximum at the inside of the coil With this fact in view, it has been suggested that the bulk of the metal in the inductor coil intendedto carry the current be concentrated near the inside of the coil, and only sufficient metal be placed near the pen hery to form the walls of suitable passa es or the cooling medium.. This has the urther advantage that in case of leakage the water will escape near the outside of the inductor, instead of at the inside, where it might produce an ex plosion.

Inductor coils previously designed to concentrate the greater part of the metal near the interior of the coil, and carry the water along the outside, have been built up by attachmg tubes to the outside of the coil, or by slotting the outside edge of the coil and securing a strip along this edge. In any case, it has been necessary that brazing,'soldering, welding or some similar means of attachment be used.

While brazing, welding, and other similar methods of attachment may be satisfactory under some conditions, I find that very freing) is avoided.

quently the inductor coil becomes highly heated. At such times these methods are likely to fail, with consequent leakage of water, which, in spite of every precaution, may come in contact with the heated crucible and cause the furnace to explode. closing an opening or joining surfaces by soltion of'the wall due to high heating of the in-.

ductor coil (below the point of actual melt- Furthermore, I obtain a much greater facility of construction and cheapness of manufacture than is possible with an inductor formed by brazing, soldering, or welding. And since the etlicien-cy of cooling of the inductor coil depends to a considerable extent upon the ease with which heat is conducted through the metal parts of the coil to the point of water cooling, my structure attains very high thermal transmission efliciency because all parts of the metal wall are in-equally intimate contact, instead of having a soldered portion, for example, which 'will conduct heat less readily.

Figure l is a vertical central section, partlyv diagrammatic, of an induction furnace to which my invention is ap lied. a

Figure 2 is an enlarge fragmentary View corresponding generally to Figure 1.

Figure 3 shows in fragmentary perspective a sectioned turn of my inductor coil.

The inductor 10 is supplied with current from a conventional power source 11 through the lines 12 and 13. Power factor correction time leaving a passage 21 formed between the end 22 of the fold 19 and the outer edge 23 of the original tubular stock. In order to permit close winding of the turns, the outer edges have been bent as at 24 and25 so that thewidth of the turn will be no greater at the outside than at the inside. 4

It will be evident that variations and modifications in the folding or crimping of the inner edge may be made to concentrate a relatively greater or relativelysmaller portion of the entire tube wall on the inner conductor portion of the turn. On the other hand, the walls of the water carrying passage 21 may be formed in any way which is desired, by varying the shape of the folds 24 and 25, or by increasing or reducing thenumber of folds, or by filleting the edges or progressively curving the walls in any of the manners familiar to designers.

I have described the method here shown as my best form because it permits close winding of the turns, with water cooling which should ordinarily be adequate, and suflicient concentration of the current carrying capac-' ity near the inside of the coil to provide for the increased current density at that point.

In view of my invention and disclosure variations and modifications to meet individ-- 1151i whim or particular need will doubtless become evident to others skilled inthe art, to obtain part or all of the benefits of my inven tion without copying the structure shown, and I, therefore, claimrall such in so far as they fall within the reasonable spirit and scope of my invention; J

Having thus describedmy invention, what I claim as new and desire'to secure by Letters Patent is: 4.

1. In \an electric induction furnace, an in ductor coil having tubularfintegral walls folded upon themselves at the inside of the coil, leaving an interior passage near the periphery of the coil. I

2. In an electric inductionfurnace, a continuous seamless tube criinped at one side to concentrate. the metal at that point, having an interior passage displaced toward the other side, and wound into a coil with the criinped edge inward.

3. In an electric induction furnace, an inductor coil of a rectangularcross section having its lateral walls crimped at the inside edge to..forn1 the inner edge of an interior passage of rectangular cross section.

FRANZ EIBL. 

